State conservation agents pinpoint trout problem in Jackson's Rotary Lake

Rotary Lake in Jackson City Park will be fully stocked with trout when the season for the cold-water fish opens Feb. 1.

The Missouri Department of Conservation pinpointed the private hatchery where the fish were raised as the source of a parasite problem that killed nearly 500 of the 1,300 trout that were stocked in the lake Oct. 30.

On Tuesday, another 500 trout from the state's hatchery, averaging one pound and about 12 to 13 inches in length, were stocked in the lake.

Shane Anderson, director of parks for Jackson, said the decision to restock the lake is welcome.

"The interest has just been a standing question, will the lake be restocked," Anderson said. "That has been answered. That is a fine amount of fish."

In December, anglers and park workers began noticing an unusually heavy death rate among the trout. An investigation found that the fish were infected with a tiny crustacean called a copepod that attaches itself to the gills and inside the mouth of the fish.

In all, 493 dead fish were collected, said Salvador Mondragon, a fisheries management assistant with the conservation agency's Cape Girardeau regional office.

Few fish have died since, and the life cycle of the copepod is long enough that the 500 trout stocked Tuesday won't be affected, Mondragon said.

"We have continued to monitor the lake to make sure all the parasites were eradicated from the lake," Mondragon said. "We were just monitoring the fish that were surviving, and we went out a couple of times to take some samples and evaluate the fish."

A fish infected with copepods will be less vigorous, and the copepods themselves look like tiny maggots on the tongue or gills. Infected fish are safe to eat, but they should be thoroughly cooked.

The fish that were infected came from a private hatchery that sells to the department, Mondragon said. While fish from the hatchery have been stocked into other lakes and streams, no other waterway beside Rotary Lake experienced a major fish kill, Mondragon said.

Catch and release

Until the opening of trout season Feb. 1, the lake is open for fishing, but anyone catching a trout must return it to the water. A fishing license is required for any fishing activity at the lake in City Park. But after Feb. 1, anglers intending to keep the fish they catch must have a trout permit as well, Mondragon said.

The trout program has been well-received in Jackson over the years, Anderson said.

Rotary Lake is stocked with trout in late fall each year when water temperatures fall enough to keep the fish alive. Trout are cold-water fish, and each spring, as water temperatures rise, any trout that survive the open season die as the water warms in the late spring and summer sun.

While the fish will not survive warm temperatures, Anderson said he has never seen any dead trout due to warm water.

"They are caught or the turtles catch them or somebody catches them," he said. "They are going to good use."

The department is still studying why the fish at Jackson's lake died while those stocked in other locations did not, Mondragon said. The fish could have been subject to stress while they were moved, or the lake could have concentrations of algae that depleted the oxygen supply.

After the evaluation is completed, he said, one possible measure would be to use a herbicide of some kind on the lake to cut down on algae growth.

rkeller@semissourian.com

388-3642

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